Superhydrophilic hydroxyapatite/hydroxypropyltrimethyl ammonium chloride chitosan composite coating for enhancing the antibacterial and corrosion resistance of magnesium alloy

Bacterial infection and excessive corrosion rate are two major concerns of Mg alloy orthopedic implants. Compared with single-function antibacterial coating, dual-function antibacterial coatings with both bacteria-resisting and bacteria-killing properties exhibit excellent performance in anti-bacterial adhesion and preventing biofilm formation. In this work, a dual-function antibacterial composite coating of hydroxyapatite (HA)/hydroxypropyltrimethyl ammonium chloride chitosan (HACC) was successfully prepared on Mg alloy by hydrothermal and electrodeposition methods. Electrochemical tests and immersion experiments have shown that the dense composite coating could provide effective protection for Mg alloy. Compared with the naked Mg alloy, the composite coating exhibited superhydrophilicity with a contact angle of 4°, which significantly reduced protein adsorption and bacterial adhesion. Meanwhile, HACC had excellent bactericidal properties, due to the presence of the quaternary ammonium groups in the molecular chain that changed bacterial cell membrane permeability. The bacterial-killing efficiency of the composite coating was 99.9% against S. aureus and 94.7% against E. coli. Moreover, the cell viability experiments indicated that the composite coating had good biocompatibility on MC3T3-E1 cells with above 84% cell viability. This work provided a strategy for designing surface coatings on Mg alloy implants with desirable corrosion resistance and antibacterial property simultaneously.